Multiple benefits of oxygen therapy for hypoxemic patients with chronic lung disease are well established. Steady flow oxygen therapy is inefficient, wasteful and has a high cost. The Oxymizer pendant improves efficiency of oxygen delivery compared with SF. However, the device requires that the patient inhale and exhale nasally to maximize its oxygen-saving properties. When patients do PLB they may not receive full oxygen-saving benefit of the pendant. Yet PLB itself can increase SaO2. We evaluated an AP, which does not require nasal exhalation, in nine patients with COPD. We measured SaO2 while breathing oxygen via SF and the AP with nasal-only breathing and PLB. Results indicate that the AP maintains an increase in SaO2 over SF during nasal-only breathing and a further increase during PLB. We conclude that AP acts as an oxygen conserver during PLB; PLB with the AP achieves greater savings than with nasal-only breathing.